feat: add type-safe native platform headers and portable drag support

- Add include/yasl/native/{wayland,cocoa,x11}.h with type-safe handle accessors.
- Unify drag-and-drop and window carry support across Wayland, X11, and Cocoa.
- Preserve full ABI compatibility for capability flags.
- Install native headers conditionally based on enabled backend.
- Include missing tablet example and backend test suites.

3 files changed, 180 insertions, 0 deletions

diff --git a/tests/cocoa/test_cursor.m b/tests/cocoa/test_cursor.m
new file mode 100644
index 0000000..0f3ba06
--- /dev/null
+++ b/tests/cocoa/test_cursor.m
@@ -0,0 +1,53 @@
+#import <AppKit/AppKit.h>
+#include <yasl/native.h>
+#include <assert.h>
+
+static void assert_transparent(NSCursor *cursor)
+{
+    assert(cursor);
+    NSBitmapImageRep *bitmap = [NSBitmapImageRep imageRepWithData:cursor.image.TIFFRepresentation];
+    assert(bitmap && bitmap.hasAlpha);
+    for (NSInteger y = 0; y < bitmap.pixelsHigh; y++)
+        for (NSInteger x = 0; x < bitmap.pixelsWide; x++)
+            assert([bitmap colorAtX:x y:y].alphaComponent == 0);
+}
+
+int main(void)
+{
+    @autoreleasepool {
+        struct yasl_display *display = yasl_display_open(NULL, NULL);
+        assert(display);
+        struct yasl_surface_spec spec = {.title = "Cursor test", .size = {320, 240}};
+        struct yasl_surface *surface = yasl_surface_create_toplevel(display, &spec);
+        assert(surface);
+        NSWindow *window = (NSWindow *)yasl_surface_get_native_handle(surface);
+        NSView *view = window.contentView;
+        yasl_surface_set_cursor(surface, YASL_CURSOR_HIDDEN);
+        [view cursorUpdate:nil];
+        NSCursor *hidden = [NSCursor currentCursor];
+        assert_transparent(hidden);
+
+        NSEvent *motion = [NSEvent mouseEventWithType:NSEventTypeMouseMoved
+            location:NSMakePoint(100, 120) modifierFlags:0 timestamp:0
+            windowNumber:window.windowNumber context:nil eventNumber:0 clickCount:0 pressure:0];
+        [view mouseMoved:motion];
+        [view cursorUpdate:nil];
+        assert([NSCursor currentCursor] == hidden);
+        struct yasl_input_event event;
+        bool moved = false;
+        while (yasl_surface_input_poll(surface, &event))
+            if (event.kind == YASL_INPUT_MOUSE && event.mouse.kind == YASL_PTR_MOTION)
+                moved = true;
+        assert(moved);
+
+        [[NSCursor arrowCursor] set]; /* Simulate leaving and re-entering. */
+        [view cursorUpdate:nil];
+        assert([NSCursor currentCursor] == hidden);
+        yasl_surface_set_cursor(surface, YASL_CURSOR_ARROW);
+        [view cursorUpdate:nil];
+        assert([NSCursor currentCursor] == [NSCursor arrowCursor]);
+        yasl_surface_destroy(surface);
+        yasl_display_close(display);
+    }
+    return 0;
+}
diff --git a/tests/cocoa/test_ownership.m b/tests/cocoa/test_ownership.m
index 168a47b..2b2f52d 100644
--- a/tests/cocoa/test_ownership.m
+++ b/tests/cocoa/test_ownership.m
@@ -1,4 +1,5 @@
 #include "yasl/native.h"
+#include "yasl/native/cocoa.h"
 #import <AppKit/AppKit.h>
 #include "yasl/yasl.h"
 #include <assert.h>
@@ -13,7 +14,10 @@ int main(void)
     struct yasl_surface *s = yasl_surface_create_toplevel(d, &spec);
     assert(s);
     assert(yasl_display_get_native_handle(d) == (void *)NSApp);
+    assert(yasl_cocoa_display_get_application(d) == NSApp);
     NSWindow *window = (NSWindow *)yasl_surface_get_native_handle(s);
+    assert(yasl_cocoa_surface_get_window(s) == window);
+    assert(yasl_cocoa_surface_get_view(s) == window.contentView);
     assert([window isKindOfClass:[NSWindow class]] && window.contentView);
     struct yasl_input_event event;
     while (yasl_surface_input_poll(s, &event)) {}
diff --git a/tests/cocoa/test_tablet.m b/tests/cocoa/test_tablet.m
new file mode 100644
index 0000000..f1489a1
--- /dev/null
+++ b/tests/cocoa/test_tablet.m
@@ -0,0 +1,123 @@
+#import <AppKit/AppKit.h>
+#include <yasl/native.h>
+#include <assert.h>
+
+/* A strict event double catches querying tablet-only properties on ordinary
+ * mouse events, and proximity-only properties on tablet point events. */
+@interface TabletSample : NSObject
+@property NSEventType type;
+@property NSEventSubtype subtype;
+@property NSEventModifierFlags modifierFlags;
+@property NSPoint locationInWindow;
+@property NSInteger buttonNumber;
+@property NSUInteger buttonMask;
+@property(getter=isEnteringProximity) BOOL enteringProximity;
+@property NSPointingDeviceType tool;
+@property float samplePressure;
+@property NSPoint sampleTilt;
+@end
+
+@implementation TabletSample
+- (float)pressure
+{
+    assert(self.type == NSEventTypeTabletPoint || self.subtype == NSEventSubtypeTabletPoint);
+    return self.samplePressure;
+}
+- (NSPoint)tilt
+{
+    assert(self.type == NSEventTypeTabletPoint || self.subtype == NSEventSubtypeTabletPoint);
+    return self.sampleTilt;
+}
+- (NSPointingDeviceType)pointingDeviceType
+{
+    assert(self.type == NSEventTypeTabletProximity || self.subtype == NSEventSubtypeTabletProximity);
+    return self.tool;
+}
+@end
+
+static struct yasl_mouse_event next(struct yasl_surface *surface)
+{
+    struct yasl_input_event event;
+    while (yasl_surface_input_poll(surface, &event))
+        if (event.kind == YASL_INPUT_MOUSE) return event.mouse;
+    assert(!"Expected a pointer event");
+    return (struct yasl_mouse_event){0};
+}
+
+int main(void)
+{
+    @autoreleasepool {
+        struct yasl_display *display = yasl_display_open(NULL, NULL);
+        assert(display && (yasl_display_caps(display) & YASL_CAP_TABLET));
+        struct yasl_surface_spec spec = {.title = "Tablet test", .size = {320, 240}};
+        struct yasl_surface *surface = yasl_surface_create_toplevel(display, &spec);
+        assert(surface);
+        NSWindow *window = (NSWindow *)yasl_surface_get_native_handle(surface);
+        NSView *view = window.contentView;
+        struct yasl_input_event event;
+        while (yasl_surface_input_poll(surface, &event)) {}
+        TabletSample *sample = [TabletSample new];
+        NSEvent *native = (NSEvent *)sample;
+        sample.type = NSEventTypeTabletProximity;
+        sample.enteringProximity = YES;
+        sample.tool = NSPointingDeviceTypePen;
+        [view tabletProximity:native];
+        sample.type = NSEventTypeMouseMoved;
+        sample.subtype = NSEventSubtypeTabletPoint;
+        sample.locationInWindow = NSMakePoint(100, 120);
+        sample.sampleTilt = NSMakePoint(-0.5, 0.5);
+        [view mouseMoved:native];
+        struct yasl_mouse_event ev = next(surface);
+        assert(ev.device == YASL_PTR_DEV_PEN && ev.kind == YASL_PTR_MOTION && !ev.pen.pressure);
+        assert(ev.pen.tilt_x == -45 && ev.pen.tilt_y == -45);
+        sample.type = NSEventTypeLeftMouseDown;
+        sample.samplePressure = 0.5;
+        [view mouseDown:native];
+        ev = next(surface);
+        assert(ev.device == YASL_PTR_DEV_PEN && ev.kind == YASL_PTR_PRESS && ev.button == 0);
+        assert(ev.pen.pressure == 32767);
+        struct yasl_vector2i position = ev.pos;
+        /* Native tablet events cover stationary pressure changes. */
+        sample.type = NSEventTypeTabletPoint;
+        sample.subtype = NSEventSubtypeMouseEvent;
+        sample.buttonMask = NSEventButtonMaskPenTip;
+        sample.samplePressure = 1.5;
+        [view tabletPoint:native];
+        ev = next(surface);
+        assert(ev.kind == YASL_PTR_MOTION && ev.pen.pressure == 65535);
+        assert(ev.pos.x == position.x && ev.pos.y == position.y);
+        sample.samplePressure = 0; /* Zero does not release a held tip button. */
+        [view tabletPoint:native];
+        assert(next(surface).kind == YASL_PTR_MOTION);
+        sample.buttonMask = 0;
+        [view tabletPoint:native];
+        ev = next(surface);
+        assert(ev.kind == YASL_PTR_RELEASE && !ev.pen.pressure && ev.device == YASL_PTR_DEV_PEN);
+        sample.type = NSEventTypeTabletProximity;
+        sample.enteringProximity = NO;
+        [view tabletProximity:native];
+        assert(next(surface).kind == YASL_PTR_LEAVE);
+        sample.enteringProximity = YES;
+        sample.tool = NSPointingDeviceTypeEraser;
+        [view tabletProximity:native];
+        sample.type = NSEventTypeTabletPoint;
+        sample.samplePressure = 0.75;
+        sample.buttonMask = NSEventButtonMaskPenTip;
+        [view tabletPoint:native];
+        ev = next(surface);
+        assert(ev.device == YASL_PTR_DEV_ERASER && ev.kind == YASL_PTR_PRESS && ev.pen.pressure > 0);
+        sample.type = NSEventTypeTabletProximity;
+        sample.enteringProximity = NO;
+        [view tabletProximity:native];
+        ev = next(surface);
+        assert(ev.device == YASL_PTR_DEV_ERASER && ev.kind == YASL_PTR_LEAVE && !ev.pen.pressure);
+        sample.type = NSEventTypeMouseMoved;
+        [view mouseMoved:native];
+        ev = next(surface);
+        assert(ev.device == YASL_PTR_DEV_MOUSE && !ev.pen.pressure);
+        [sample release];
+        yasl_surface_destroy(surface);
+        yasl_display_close(display);
+    }
+    return 0;
+}